/Engine/Source/Runtime/Engine/Classes/Materials/MaterialExpression.h
Called after a node copy, once the Material and Function properties are set correctly and that all new expressions are added to Material->Expressions
virtual void PostCopyNode ( const [TArray](API\Runtime\Core\Containers\TArray)< [UMaterialExpression](API\Runtime\Engine\Materials\UMaterialExpression) * > & CopiedExpressions )